Stent

ABSTRACT

A radially expandable stent comprising a plurality of spaced band-like elements and intersecting links is disclosed. The band-like elements have a generally serpentine configuration to provide continuous waves of generally sinusoidal character to each band-like element. The waves are characterized by a plurality of peaks and troughs taking a generally longitudinal direction along the cylinder such that the waves in the band-like elements open as the stent is expanded from a first diameter to a second diameter. The intersecting links are substantially U-shaped and terminate in first and second shanks. The first shank of a link emanates from a region between a peak and trough on a band-like element and the second shank of the link emanates from a region between a peak and trough on an adjacent band-like element.

FIELD OF THE INVENTION

This invention relates to an endoprosthesis device for implantationwithin a body vessel, typically a blood vessel. More specifically, itrelates to a tubular expandable stent of improved longitudinalflexibility.

BACKGROUND OF THE INVENTION

Stents are placed or implanted within a blood vessel for treatingstenoses, strictures or aneurysms therein. They are implanted toreinforce collapsing, partially occluded, weakened, or dilated sectionsof a blood vessel. They have also been implanted in the urinary tractand in bile ducts.

Typically, a stent will have an unexpanded (closed) diameter forplacement and an expanded (opened) diameter after placement in thevessel or the duct. Some stents are self-expanding and some are expandedmechanically with radial outward force from within the stent, as byinflation of a balloon.

An example of the latter type is shown in U.S. Pat. No. 4,733,665 toPalmaz, which issued Mar. 29, 1988, and discloses a number of stentconfigurations for implantation with the aid of a catheter. The catheterincludes an arrangement wherein a balloon inside the stent is inflatedto expand the stent by plastically deforming it, after positioning itwithin a blood vessel.

A type of self-expanding stent is described in U.S. Pat. No. 4,503,569to Dotter which issued Mar. 12, 1985, and discloses a shape memory stentwhich expands to an implanted configuration with a change intemperature. Other types of self-expanding stents not made of shapememory material are also known.

This invention is directed to stents of all these types when configuredso as to be longitudinally flexible as described in detail hereinbelow.Flexibility is a desirable feature in a stent so as to conform to bendsin a vessel. Such stents are known in the prior art. Examples are shownin U.S. Pat. No. 4,856,516 to Hillstead; U.S. Pat. No. 5,104,404 toWolff; U.S. Pat. No. 4,994,071 to MacGregor; U.S. Pat. No. 5,102,417 toPalmaz; U.S. Pat. No. 5,195,984 to Schatz; U.S. Pat. No. 5,135,536 toHillstead; U.S. Pat. 5,354,309 to Shepp-Pesch et al.; EPO PatentApplication 0 540 290 A2 to Lau; EPO Patent Application No. 0 364 787 B1to Schatz, and PCT Application WO 94/17754 (also identified as GermanPatent Application 43 03 181).

Generally speaking, these kinds of stents are articulated and areusually formed of a plurality of aligned, expandable, relativelyinflexible, circular segments which are interconnected by flexibleelements to form a generally tubular body which is capable of a degreeof articulation or bending. Unfortunately, a problem with such stents isthat binding, overlapping or interference can occur between adjacentsegments on the inside of a bend due to the segments moving toward eachother and into contact. Moreover, on the outside of a bend, the segmentscan move away from each other, leaving large gaps. This can lead toimproper vessel support, vessel trauma, flow disturbance, kinking,balloon burst during expansion, and difficult recross for devices to beinstalled through already implanted devices and to unsupported regionsof vessel.

A diamond configuration with diagonal connections between each and everydiamond of each segment is also known but such closed configurationslack flexibility.

Such stents also suffer from the problem of shortening upon radialexpansion. As the stent expands radially, it contracts lengthwise.

It is an object of this invention to provide a stent with a distributedstructure which is longitudinally flexible that avoids these problemsand exhibits improved flexibility in the stent body segments thereofrather than in flexible joints between the segments. It is a furtherobject to provide stents that exhibit a desired lengthening or a desiredshortening on radial expansion as well as stents which exhibitsubstantially no shortening or lengthening on radial expansion.

It is a further object of the present invention to provide a stentformed of a series of interconnected flexible cells.

It should be noted that for the purposes of this invention, the phrasegenerally sinusoidal is intended to include waves characterized by sineand cosine functions as well as waves which are not rigorouslycharacterized by those functions, but nevertheless resemble such waves.In a more general way, such waves include those which are characterizedas having one or more peaks and troughs. As an example, a wave whosepeaks and troughs are U shaped or bulbous is intended to be included.Also intended to be included, without limiting the definition, are waveswhich are more triangular in shape such as a saw-tooth wave or waveswhose peaks and troughs are rectangular.

SUMMARY OF THE INVENTION

The present invention provides a radially expandable stent having firstand second ends and a longitudinal axis. The stent comprises a pluralityof spaced band-like elements forming a hollow cylinder. The band-likeelements are arranged sequentially along the cylinder and each band-likeelement comprises one or more sub-elements having a generally serpentineconfiguration to provide continuous waves to each sub-element. The wavesare characterized by a plurality of peaks and troughs taking a generallylongitudinal direction along the cylinder such that the waves in thesub-elements open as the stent is expanded from a first diameter to asecond diameter. Adjacent band-like elements in the stent are connectedtogether by one or more links. Each link has at least one bend thereinand terminates in first and second shanks. The first shank of each linkemanates from a region of attachment between a peak and trough on asub-element of a band-like element while the second shank of each linkemanates from a region of attachment between a peak and trough on asub-element of an adjacent band-like element. The first shanks attachedto any given sub-element of a band-like element are spaced substantiallyone wavelength or more apart along the sub-element of a band-likeelement. Likewise, the second shanks attached to any given sub-elementof a band-like element are spaced substantially one wavelength or moreapart along the sub-element of the band-like element.

The present invention is also directed to a radially expandable stentcomprising a plurality of spaced band-like elements forming a hollowcylinder. The band-like elements are arranged sequentially along thecylinder. Each band-like element has a generally serpentineconfiguration to provide continuous waves of generally sinusoidalcharacter to each band-like element. The waves are characterized by aplurality of peaks and troughs taking a generally longitudinal directionalong the cylinder, the peaks and troughs having a midpoint regionmidway between them, such that the waves in the band-like elements openas the stent is expanded from a first diameter to a second diameter. Thestent further comprises one or more spaced generally longitudinalelements extending from the first end of the stent to the second end ofthe stent and having alternating peaks and troughs and longitudinaltransition regions midway between adjacent peaks and troughs. Adjacentlongitudinal elements are in phase with one another. Each generallylongitudinal element intersects each band-like element in a region ofintersection, which includes a region between a peak and a trough on aband-like element, and a transition region of a longitudinal element.Adjacent longitudinal elements intersect each band-like element at leastone wavelength apart along the band-like element.

The present invention is further directed to an expandable stent whichin expanded form comprises a plurality of flexible connected primarycells. Each primary cell comprises a first member having first andsecond ends extending in a direction generally perpendicular to thelongitudinal axis of the stent and having a serpentine shape. The firstmembers each have one peak and one trough, the peak and trough taking agenerally longitudinal direction along the stent. Each primary cellfurther comprises a second member having first and second ends extendingin a direction generally perpendicular to the longitudinal axis, andhaving a serpentine shape. The second members have one peak and onetrough, the peak and trough taking a generally longitudinal directionalong the stent. The second member is situated generally opposite thefirst member and is optionally out of phase with the first member. Theprimary cells also comprise a first link having a first end and a secondend, and extending in a generally longitudinal direction. The first linkhas at least one bend therein and is disposed between the first end ofthe first member and the first end of the second member. The first endof the first link is attached to the first end of the first member andthe second end of the first link is attached to the first end of thesecond member. Finally, each primary cell comprises a second link havinga first end and a second end, extending in a generally longitudinaldirection. The second link has at least one bend therein and is disposedbetween the second end of the first member and the second end of thesecond member. The first end of the second link is attached to secondend of the first member and the second end of the second link isattached to the second end of the second member. The second link is inphase with the first link. The primary cells are arranged in one or moreprimary bands and adjacent primary bands are interconnected. Primarycells in adjacent bands may optionally be offset relative to one anotheralong the bands.

Optionally, the stent may further comprise secondary bands comprised ofsecondary cells, the secondary bands alternating with the primary bands.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a tubular, unexpanded stent according to the invention.

FIG. 2 shows a flat view of the pattern used in the stent shown in FIG.1.

FIG. 3 shows an expanded stent of the configuration shown in FIG. 1.

FIG. 4 a shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 4 b shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 4 c shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 4 d shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 4 e shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 4 f shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 4 g shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 4 h shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 4 i shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 5 shows an enlarged view of the circled region in FIG. 4 a.

FIG. 6 a shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 6 b shows an expanded stent of the configuration shown in FIG. 6 a.

FIG. 6 c shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 7 a shows a flat view of an alternate unexpanded stentconfiguration according to the invention.

FIG. 7 b shows an expanded stent of the configuration shown in FIG. 7 a.

FIG. 8 shows a flat view of an alternate unexpanded stent configurationaccording to the invention.

FIG. 9 shows a flat view of an alternate unexpanded stent configurationaccording to the invention.

FIG. 10 shows a flat view of an alternate unexpanded stent configurationaccording to the invention.

FIG. 11 shows a flat view of an alternate unexpanded stent configurationaccording to the invention.

FIG. 12 shows a flat view of an alternate unexpanded stent configurationaccording to the invention.

FIG. 13 shows a flat view of an alternate unexpanded stent configurationaccording to the invention.

FIG. 14 shows a flat view of an alternate unexpanded stent configurationaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific preferred embodiments of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiments illustrated.

For the sake of consistency, the terms ‘peak’ and ‘trough’ shall bedefined with respect to the proximal and distal ends of the stent. Asseen in the Figures, each of the stents has a proximal end designated bya numeral ending in 73 (e.g., 173) and a distal end designated by anumeral ending in 74 (e.g. 174). Peaks are concave relative to theproximal end of the stent and convex relative to the distal end of thestent. Troughs, on the other hand, are convex relative to the proximalend of the stent and concave relative to the distal end of the stent.

Moreover, for the sake of clarity, the terms ‘peak’ are ‘trough’ inreference to a band-like element or sub-element are intended to includenot only the point(s) of maximum or minimum amplitude on a band-likeelement, but also a small region around the maximum or minimum. Moreprecisely, in the case of peaks, the ‘small region’ around the maximumis intended to include any point along the band-like element which isdistal of a line extending through the innermost part of the band-likeelement at the maximum amplitude and perpendicular to the longitudinalaxis of the stent up to the peak itself. In the case of troughs, the‘small region’ around the minimum is intended to include any point alongthe band-like element which is proximal of a line extending through theinnermost part of the band-like element at the minimum amplitude andperpendicular to the longitudinal axis of the stent up to the troughitself. As seen in FIG. 1, each peak 124 has an innermost part of thepeak 125 which lies on the inside of the band-like element opposite thepeak and each trough 128 has an innermost part 127. Peak region 131,shaded for illustrative purpose in one instance, is seen to be thatregion of the band-like element that extends distal to innermost part125 and line 131 extending through innermost part 125 perpendicular tolongitudinal axis 101. Similarly trough region 133 shaded forillustrative purpose in one instance, is seen to be that region of theband-like element that extends proximal to innermost part 127 and line129 extending through innermost part 127 perpendicular to longitudinalaxis 101.

Turning to the Figures, FIG. 2 shows generally at 105 a fragmentary flatview of an unexpanded stent configuration. An actual inventive tubularstent in unexpanded form is shown generally at 110 in FIG. 1. The stentis shown for clarity in FIG. 2 in the flat and may be made from flatpattern 105, shown generally in FIG. 2, which is formed into a tubularshape by rolling the pattern so as to bring edges 112 and 114 together.The edges may then be joined as by welding or the like to provide aconfiguration such as that showed in FIG. 1. The stent may also beformed of a laser-cut tube.

The configuration can be seen in these Figures to be made up of aplurality of spaced band-like elements, generally indicated at 116,forming a hollow cylinder 120. Band-like elements 116 comprise one ormore sub-elements. In the embodiment shown in FIG. 2, each band-likeelement 116 is formed of one sub-element 117 although in otherembodiments the band-like elements may be formed of multiplesub-elements. Sub-elements 117 are arranged sequentially along cylinder120, as shown in FIG. 1. Each sub-element 117 has a generally serpentineconfiguration to provide continuous waves of generally sinusoidalcharacter to each sub element 117, the waves being characterized by aplurality of peaks 124 and troughs 128 taking a generally longitudinaldirection along cylinder 120. As the stent is expanded from a firstdiameter to a second diameter, the waves in sub-elements open.

The inventive stents further comprise a plurality of links, each linkhaving at least one bend therein. In the embodiment of FIG. 2, U-shapedlinks 132 connect adjacent band-like elements 116 together. Althoughsubstantially U-shaped, links 132 may be rounded or square or pointed orthe like. As shown in FIGS. 1-3, links 132 extending between adjacentbands 116 are arranged to form rows 142 of links 132. Links in adjacentrows are 180° out of phase with one another. Links 132 terminate infirst 136 and second 140 shanks. As shown in FIG. 2, the first shank 136of a link 132 emanates from a region 133 between a peak 124 and trough128 on a band-like element 116 and the second shank 140 of the link 132emanates from a region 135 between a peak 124 and trough 128 on anadjacent band-like element. First shanks 136 attached to any givensub-element of a band-like element are spaced substantially onewavelength apart along the sub-element of the band-like element andsimilarly, second shanks 140 attached to any given sub-element of aband-like element are spaced substantially one wavelength apart alongthe sub-element of the band-like element.

Although first shank 136 and second shank 140 are substantiallyperpendicular to the bands in the region of intersection between theshanks and the bands as depicted in FIGS. 1-2, this is not a requirementof the invention. As such, the first and second shanks may be angled atsome other acute angle.

A minimum of one link 132 is required to connect adjacent band-likeelements. Preferably, there will be a one-to-one correspondence betweenlinks and peaks (or troughs). Of course, any number of linksintermediate between 1 and the number requisite for a one-to-onecorrespondence of peaks (troughs) and links may be used as well to joinadjacent band-like elements.

For the sake of completeness, the stent of FIG. 2 is shown generally at110 in FIG. 3 in its expanded state. As shown in FIG. 3, the ‘U’ shapedlinks assume an ‘M’ shape as a result of the expansion of the stent. The‘M’ shaped links are shown at 148.

The stent of FIGS. 1-3 may also be seen to be formed of a plurality ofband-like elements 116 and a plurality of spaced generally longitudinalelements 172 (one of which is highlighted for clarity in FIG. 2). Asshown in FIG. 2, longitudinal elements 172 extend from the first end 173of the stent to the second end 174 of the stent and have alternatingpeaks 175 and troughs 176 and longitudinal transition regions 177 midwaybetween adjacent peaks 175 and troughs 176. Adjacent longitudinalelements 172 are in phase with one another. Each generally longitudinalelement 172 intersects each band-like element 116 in a region ofintersection 178, the region of intersection including a region betweena peak and a trough on a band-like element, and a transition region 177of a longitudinal element 172.

The stent, as seen in FIGS. 1 and 2, may also seen to be comprised of aplurality of flexible connected primary cells 180. Each primary cell 180has a first member 181 having first 182 and second 183 ends extending ina direction generally perpendicular to the longitudinal axis. Firstmember 181 has a serpentine shape with one peak 124 and one trough 128.Peak 124 and trough 128 take a generally longitudinal direction alongthe stent. Each primary cell 180 further has a second member 184 havingfirst 185 and second 186 ends and extending in a direction generallyperpendicular to the longitudinal axis. Second member 184 has aserpentine shape and has one peak 124 and one trough 128. Peak 124 andtrough 128 take a generally longitudinal direction along the stent.Second member 184 is situated generally opposite first member 181, andis out of phase with first member 181 by 180°. Extending between firstmember 181 and second member 184 is a first link 187 having a first end188 and a second end 189. First link 187 extends in a generallylongitudinal direction, and has at least one bend therein. First end 188of first link 187 is attached to first end 182 of first member 181.Second end 189 of first link 187 is attached to first end 185 of secondmember 184. Finally, extending between first member 181 and secondmember 184, and parallel to first link 187 is second link 190 having afirst end 191 and a second end 192. First end 191 of second link 190 isattached to second end 183 of first member 181 and second end 192 ofsecond link 190 is attached to second end 186 of second member 184.Second link 190 is in phase with first link 187. Primary cells 180 arearranged in one or more primary bands, shown generally at 193 andadjacent primary bands are interconnected.

Although first shank 136 and second shank 140 of links 132 are depictedin FIG. 2 as extending from regions substantially opposite each other onadjacent band-like elements, the regions need not be substantiallyopposite one another but rather, may be displaced relative to oneanother on their respective band-like elements. Depending on thecircumferential displacement between the first and second shanks of agiven link, and the relative phasing of adjacent band-like elements, thefirst and second shanks will either be oriented substantially in thesame direction or substantially in the opposite direction. For the sakeof this invention, first shanks 136 and second shanks 140 associatedwith links 132 as shown in FIG. 2 are considered to be oriented insubstantially the same direction. Both shanks are oriented upward.

In FIG. 4 a, on the other hand, first shanks 236 a and second shanks 240a of each link 232 a are considered to be oriented in substantiallyopposite directions. One shank is oriented upward while the other shankis oriented downward. In the specific embodiment shown in FIG. 4 a,first shank 236 a of each link 232 a extends from a first region 244 aon a first band-like element 252 a and second shank 240 a of each link232 a extends from a second region 248 a on an adjacent band-likeelement 256 a, with second region 248 a situated opposite a region onehalf wavelength further along first band-like element 252 a from firstregion 244 a. Of course, the half wavelength separation of FIG. 4 a ismeant to be exemplary of a more general class of stents in which oneshank of a link is oriented upward and one shank of a link is orienteddownward. As such, other separations between the regions of attachmentof the first and second shanks are contemplated as well.

FIGS. 4 b-f show embodiments in which first and second shanks areoriented in substantially the same direction, as in FIG. 2, and in whichthe first and second shanks of a link are displaced circumferentially.In the embodiment shown in FIG. 4 b, first shank 236 b of each link 232b extends from a first region 244 b on a first band-like element 252 band second shank 240 b of each link 232 b extends from a second region248 b on an adjacent band-like element 256 b, with second region 248 bsituated opposite a region one wavelength further along first band-likeelement 252 b from first region 244 b. All links 232 b are similarlyoriented. In the embodiment shown in FIG. 4 c, first shank 236 c of eachlink 232 c extends from a first region 244 c on a first band-likeelement 252 c and second shank 240 c of each link 232 c extends from asecond region 248 c on an adjacent band-like element 256 c, with secondregion 248 c situated opposite a region two wavelengths further alongfirst band-like element 252 c from first region 244 c. As in FIG. 4 b,all links 232 c are similarly oriented. In the embodiment shown in FIG.4 d, first shank 236 d of each link 232 d extends from a first region244 d on a first band-like element 252 d and second shank 240 d of eachlink 232 d extends from a second region 248 d on an adjacent band-likeelement 256 d, with second region 248 d situated opposite a region onewavelength further along first band-like element 252 d from first region244 d. FIG. 4 d differs from FIG. 4 b in that adjacent rows of links 233d and 235 d are out of phase with one another in FIG. 4 d where they arein phase in FIG. 4 b. In the embodiment shown in FIG. 4 e, first shank236 e of each link 232 e extends from a first region 244 e on a firstband-like element 252 e and second shank 240 e of each link 232 eextends from a second region 248 e on an adjacent band-like element 256e, with second region 248 e situated opposite a region one wavelengthfurther along first band-like element 252 e from first region 244 e. Asin FIG. 4 d, adjacent rows of links 233 e and 235 e are out of phasewith one another. It should also be noted that in the pattern in FIG. 4e, unlike in FIG. 4 d, links 232 e are seen to form a continuous pathacross the stent from first end 273 e to second end 274 e of the stent.

In the embodiment shown in FIG. 4 f, first shank 236 f of each link 232f extends from a first region 244 f on a first band-like element 252 fand second shank 240 f of each link 232 f extends from a second region248 f on an adjacent band-like element 256 f, with second region 248 fsituated opposite a region one wavelength further along first band-likeelement 252 f from first region 244 f. Adjacent rows of links 233 f and235 f are out of phase with one another. It should also be noted that inthe pattern in FIG. 4 f, links 232 f are seen to form a continuoussubstantially helical path across the stent from first end 273 f tosecond end 274 f of the stent.

In the embodiment shown in FIG. 4 g, first shank 236 g of each link 232g extends from a first region 244 g on a first band-like element 252 gand second shank 240 g of each link 232 g extends from a second region248 g on an adjacent band-like element 256 g, with second region 248 gsituated opposite a region one-half wavelength further along firstband-like element 252 g from first region 244 g. Adjacent rows of links233 g and 235 g are out of phase with one another.

In the embodiment shown in FIG. 4 h, first shank 236 h of each link 232h extends from a first region 244 h on a first band-like element 252 hand second shank 240 h of each link 232 h extends from a second region248 h on an adjacent band-like element 256 h, with second region 248 hsituated opposite a region one-half wavelength further along firstband-like element 252 h from first region 244 h. Links in adjacent rowsof links 233 h and 235 h are similarly oriented. It should also be notedthat in the pattern in FIG. 4 h, links 232 h are seen to form acontinuous helical path across the stent from first end 273 h to secondend 274 h of the stent.

Finally, FIG. 4 i presents an embodiment which is a mirror image of thestent of FIG. 4 h. First shank 236 i of each link 232 i extends from afirst region 244 i on a first band-like element 252 i and second shank240 i of each link 232 i extends from a second region 248 i on anadjacent band-like element 256 i, with second region 248 i situatedopposite a region one-half wavelength further along first band-likeelement 252 i from first region 244 i. Links in adjacent rows of links233 i and 235 i are similarly oriented. It should also be noted that inthe pattern in FIG. 4 i, links 232 i are seen to form a continuoushelical path across the stent from first end 273 i to second end 274 iof the stent.

FIGS. 4 g-i are similar to FIG. 4 a in that one shank of a link isoriented upward and one shank of a link is oriented downward.

As in FIGS. 1-3, in the embodiments of FIGS. 4 a-i, each band-likeelement consists of one sub-element and as such, the sub-element isindistinguishable from the band-like element. Further, as in the stentof FIGS. 1-3, the links in adjacent rows of links in FIGS. 4 a and 4 dare 180° out of phase with one another. In FIGS. 4 b and 4 c, on theother hand, the links in adjacent rows of links are in phase with oneanother.

The stent of FIG. 4 a may also seen to be formed of a plurality ofband-like elements 216 a and a plurality of spaced generallylongitudinal elements 272 a (one of which is highlighted, for the sakeof clarity). Longitudinal elements 272 a extending from the first end273 a of the stent to the second end 274 a of the stent and havingalternating peaks 275 a and troughs 276 a and longitudinal transitionregions 277 a midway between adjacent peaks 275 a and troughs 276 a.Adjacent longitudinal elements 272 a are in phase with one another. Eachgenerally longitudinal element 272 a intersects each band-like element216 a in a region of intersection 278 a, the region of intersectionincluding a region between a peak and a trough on a band-like element,and a transition region 277 a of a longitudinal element 272 a.Longitudinal elements 272 a are seen to proceed across the stent in agenerally diagonal fashion.

FIG. 5 shows an enlarged portion of the pattern shown in FIG. 4 a. Link232 extends from a region 233 on a band-like element substantiallymidway between a peak 224 and an adjacent trough 228 to a region 235substantially midway between a peak 224 and an adjacent trough 228 on anadjacent band-like element.

In another embodiment, as shown generally at 310 a in FIG. 6 a, links inadjacent rows are in phase with one another. Links 332 a extendingbetween adjacent band-like elements 316 a are arranged to form rows 342a of links 332 a. The links, in this case, are all identically oriented.Of course, other arrangements are possible as well, such as alternatingthe phase of the links by 180 degrees every ‘n’th row where n is aninteger, or having a block of rows with the links oriented in one wayfollowed by a block of rows with the links oriented in the oppositedirection.

FIG. 6 b shows a tubular stent formed with the pattern of FIG. 6 a,after expansion. The stent, shown generally at 310 b comprises links 332b extending between adjacent band-like elements 316 b are arranged toform rows 342 b of links 332 b which are all identically oriented. Thestent of FIG. 6 b may also be seen to be formed of a plurality ofinterconnected cells 380 b, each cell having a first corner 381 b, asecond corner 382 b, a third corner 383 b and a fourth corner 384 b. Thethird and fourth corners of primary cells and the first and secondcorners of abutting primary cells in adjacent bands are displacedrelative to one or another by half a primary cell so that as onetraverses the stent from proximal end 373 b to distal end 374 b, thecells are staggered. As seen in FIG. 6 b, each cell 380 b is oriented ina direction substantially parallel to the longitudinal axis. Stateddifferently, links 332 b which form the sides of cells 380 b areoriented in a overall direction substantially parallel to thelongitudinal axis minimizing torsional stresses within the stent.

In another embodiment, as shown in FIG. 6 c, the stent, shown generallyat 310 c in flat pattern, is similar to the stent of FIG. 6 a. The stentis formed of interconnected band-like elements 316 c (in this embodimentthe band-like element is identical to the sub-element, there being onlyone sub-element). Band-like elements 316 c are wave-like, having peaks324 c and troughs 328 c. Adjacent band-like elements 316 c areinterconnected by substantially ‘U’ shaped links 332 c. The links 332 cthat interconnect a given set of adjacent band-like elements 316 c forma row 342 c. The stent is comprised of one or more of such rows. Thestent of FIG. 6 c differs, however, from the stent of FIG. 6 a in twoaspects. First, adjacent rows 342 c of links 332 c are 180° out of phasewith one another. And second, the first shank 336 c of each link 332 cextends from a first region of intersection 355 c on a band-like element316 c and the second shank 340 c of each link 332 c extends from aregion of intersection 360 c on an adjacent band-like element 316 c, theregion of intersection 360 c on the adjacent band-like element 316 csituated opposite a region 370 c one half wavelength further along thefirst band-like element from the first region of intersection 355 c.

The stent of FIG. 6 c may also be seen to be formed of a plurality ofinterconnected cells 380 c, each cell having a first corner 381 c, asecond corner 382 c, a third corner 383 c and a fourth corner 384 c. Thethird and fourth corners of primary cells and the first and secondcorners of abutting primary cells in adjacent bands are displacedrelative to one or another by half a primary cell so that as onetraverses the stent from proximal end 373 c to distal end 374 c, thecells are staggered. Although not shown, the cells of a tubular stentformed according to the pattern of FIG. 6 c, upon expansion of the stentare oriented in a direction which is skewed relative to the longitudinalaxis of the stent, leading to torsional stresses within the stent.

In another embodiment, as shown in FIG. 7 a, the stent in flat form,shown generally at 405 a is seen to be made up of a plurality of spacedband-like elements, generally indicated at 416 a consisting of onesub-element. In the present embodiment, the sub-element is identical tothe band-like element. The stent comprises end band-like elements 417 alocated at either end of the stent and intermediate band-like elements418 a disposed between end band-like elements 417 a. Each band-likeelement 416 a has a generally serpentine configuration to providecontinuous waves of generally sinusoidal character to each band-likeelement 416 a, the waves being characterized by a plurality of peaks 424a and troughs 428 a taking a generally longitudinal direction along thestent. As the stent is expanded from a first diameter to a seconddiameter, the waves in band-like elements open. The stent furthercomprises a plurality of substantially U-shaped links 432 a connectadjacent band-like elements 416 a together. Links 432 a extendingbetween adjacent band-like elements 416 a are arranged to form rows 442a of links 432 a. Links in adjacent rows are 180° out of phase with oneanother. Links 432 a terminate in first 436 a and second 440 a shanks.

For each first shank 436 a attached to an intermediate band-like element418 a between a peak 424 a and a trough 428 a, there is a second shank440 a across the intermediate band-like element 418 a and displaced fromfirst shank 436 a and located between the same peak and trough as isfirst shank 436 a. First shanks 436 a attached to any given band-likeelement 416 a are spaced substantially one wavelength apart along theband-like element and similarly, second shanks 440 a attached to anygiven band-like element 416 a are spaced substantially one wavelengthapart along the band-like element.

The stent of FIG. 7 a may also seen to be formed of a plurality ofband-like elements 416 a and a plurality of spaced generallylongitudinal elements 472 a (one of which is highlighted for the sake ofclarity). Longitudinal elements 472 a extending from the first end 473 aof the stent to the second end 474 a of the stent and having alternatingpeaks 475 a and troughs 476 a and longitudinal transition regions 477 amidway between adjacent peaks 475 a and troughs 476 a. Adjacentlongitudinal elements 472 a are in phase with one another. Eachgenerally longitudinal element 472 a intersects each band-like element416 a in a region of intersection 478 a, the region of intersectionincluding a region between a peak and a trough on a band-like element,and a transition region 477 a of a longitudinal element 472 a.

FIG. 7 b shows a tubular stent generally at 410 b, the stent formed ofthe configuration of FIG. 7 a, in expanded form. The expanded stent isseen to comprise band-like elements 416 b joined together by links 432b. Links 432 b correspond to the substantially U-shaped links 432 a ofthe unexpanded stent and are seen to open upon expansion of the stent.

In the expanded form, the stent can also clearly be seen to comprise aplurality of interconnected cells 480 b, each cell having a first corner481 b, a second corner 482 b, a third corner 483 b and a fourth corner484 b. Links 432 b forming the sides of cells 480 b are seen to besubstantially parallel to the longitudinal axis. As such, each cell issubstantially aligned in the longitudinal direction. The third andfourth corners of primary cells and the first and second corners ofabutting primary cells in adjacent bands are displaced only slightlyrelative to one or another so that as one traverses the stent fromproximal end 473 b to distal end 474 b, the progression of cells fromone end to the other end is slightly skewed relative to the longitudinalaxis of the stent due to an artifact associated with the expansion ofthe balloon used to expand the stent.

In another embodiment shown in FIG. 8 the stent, shown generally at 510,is similar to the stent of FIG. 6 c, differing, however, in one aspect.Links 532 connecting adjacent band-like elements 516 are zig-zag shaped.As with the stent of FIG. 7, the phase of links 532 in adjacent rows 542differs by 180°. Similarly, first shanks 536 and second shanks 540 areseparated by a half of a wavelength along each of the intermediateband-like elements 517. Intermediate band-like elements are defined asthe band-like elements between the first band-like element 516 in thestent and the final band-like element 516 in the stent.

The stent of FIG. 8 is also seen to be formed of primary cells 580consisting of first member 581 and second member 584 joined together byfirst link 587 and second link 590. First link 587 and second link 590are seen to be parallel.

In yet another embodiment shown in FIG. 9, the stent in flat form, showngenerally at 605 is seen to be made up of a plurality of spacedband-like elements, 616 consisting of two interconnected sub-elements617 and 618. Each sub-element 617 and 618 has a generally serpentineconfiguration. Sub-elements 617 and 618 are arranged 180° out of phaserelative to one another, peaks 621 of first sub-elements 617 connectedto troughs 623 of second sub-elements 618 so as to form band-likeelements 616. Adjacent band-like elements 616 are in phase with oneanother and are interconnected by “U” shaped links 632. As with thestent of FIG. 6 b, the first shank 636 of each link 632 extends from afirst region of intersection 655 on a band-like element 616 and thesecond shank 640 of each link 632 extends from a region of intersection660 on an adjacent band-like element 616, the region of intersection 660on the adjacent band-like element 616 situated opposite a region 670 onehalf wavelength (based on the wavelength of the band-like element)further along the first band-like element from the first region ofintersection 655.

The stent of FIG. 9 is also seen to be formed of primary cells 680consisting of first member 681 and second member 684 joined together byfirst link 687 and second link 690. First link 687 and second link 690are seen to be parallel. Primary cells 680 are arranged in primary bandsshown generally at 693 and are interconnected with diamond shapedsecondary cells 694, arranged in secondary bands, shown generally at695. Primary 693 and secondary bands 694 alternate along the length ofthe stent.

While adjacent band-like elements are depicted in FIGS. 1-9 as being outof phase with one another by 180°, adjacent band-like elements may be inphase, as shown in FIG. 10-14 or may have their phases differ byintermediate amounts. FIG. 10 shows a portion of an inventive stent inthe flat. As seen in FIG. 10, first shank 736 of each link 732 extendsfrom a first region 744 on a first band-like element 752 and secondshank 740 of each link 732 extends from a second region 748 on anadjacent band-like element 756, with second region 748 situatedsubstantially opposite first region 744. First shanks 736 and secondshanks 740 of each link 732, however, are oppositely oriented. Links inadjacent rows of links 733 and 735 are similarly oriented. It shouldalso be noted that in the pattern in FIG. 10, links 732 are seen to forma continuous path across the stent from first end 773 to second end 774of the stent.

FIG. 11 shows a portion of an inventive stent in the flat. As seen inFIG. 11, first shank 836 of each link 832 extends from a first region844 on a first band-like element 852 and second shank 840 of each link832 extends from a second region 848 on an adjacent band-like element856, with second region 848 situated substantially opposite first region844. First shanks 836 and second shanks 840 of each link 832, however,are oppositely oriented. Links in adjacent rows of links 833 and 835 aresimilarly oriented. It should also be noted that in the pattern in FIG.11, links 832 are seen to form a continuous path across the stent fromfirst end 873 to second end 874 of the stent.

FIG. 12 shows a portion of an inventive stent in the flat. As seen inFIG. 12, first shank 936 of each link 932 extends from a first region944 on a first band-like element 952 and second shank 940 of each link932 extends from a second region 948 on an adjacent band-like element956, with second region 948 situated substantially opposite first region944. First shanks 936 and second shanks 940 of each link 932, however,are oppositely oriented. Links in adjacent rows of links 933 and 935 aresimilarly oriented. It should also be noted that in the pattern in FIG.12, links 932 are seen to form a continuous path across the stent fromfirst end 973 to second end 974 of the stent.

FIG. 13 shows a portion of an inventive stent in the flat. As seen inFIG. 13, first shank 1036 of each link 1032 extends from a first region1044 on a first band-like element 1052 and second shank 1040 of eachlink 1032 extends from a second region 1048 on an adjacent band-likeelement 1056, with second region 1048 situated substantially oppositefirst region 1044. First shanks 1036 and second shanks 1040 of each link1032 are similarly oriented but displaced circumferentially by aboutone-half wavelength along band-like elements 1052 and 1056. Links inadjacent rows of links 1033 and 1035 are out of phase with one another.

FIG. 14 shows a portion of an inventive stent in the flat. As seen inFIG. 14, first shank 1136 of each link 1132 extends from a first region1144 on a first band-like element 1152 and second shank 1140 of eachlink 1132 extends from a second region 1148 on an adjacent band-likeelement 1156, with second region 1148 situated substantially oppositefirst region 1144. First shanks 1136 and second shanks 1140 of each link1132 are similarly oriented. Links in adjacent rows of links 1133 and1135 are similarly oriented.

Although FIGS. 1-9 show a one to one correspondence between peaks andlinks, in a more general sense, fewer links may be used. For example,there may be one link for every two peaks. There must, however, be atleast one link between every two adjacent bands. Stated differently,while in the embodiments shown in the figures the links are separated byone wavelength along the band-like elements, separations of greater thana wavelength including integral and non-integral wavelength separationsare contemplated. As such, the number of links between any two adjacentbands will range from one link to the number of multiples of awavelength that are present in the band-like element. Similarly thenumber of spaced generally longitudinal elements may range from one tothe number of multiples of a wavelength that are present in theband-like element.

Further, while it is preferable for the band-like elements to be evenlyspaced apart, it is not necessary. In the case where the bands are notevenly spaced, that is, different sets of adjacent bands are separatedby different distances, the links may have differing wingspans (i.e. thedistance from first shank to second shank). Moreover, even where thebands are evenly spaced apart, the links may have differing wingspansdepending on where the shanks intersect the band-like elements.

It is understood that the present invention also contemplatessubstituting ‘U’ shaped links for zig-zag shaped links and vice versa aswell as links with one or more bends therein. As such, the links shownin the various figures are all interchangeable, allowing for minormodifications to allow for the requisite orientation of the shanks.Preferably, the links will exhibit a degree of flexibility, therebycontributing to the overall flexibility of the cells.

Although most of the figures show the inventive stents in the flat forclarity, it is understood that the stents may be formed into as tubularshape by rolling the flat patterns shown about the longitudinal axis soas to bring the edges and together, as shown in FIG. 2. The edges maythen be joined as by welding or the like to provide a configuration suchas that showed in FIG. 2. The stents may also be formed of a laser-cuttube.

The invention further contemplates a radially expandable stent havingfirst and second ends and comprising a plurality of spaced band-likeelements forming a hollow cylinder, and a plurality of spaced generallylongitudinal elements intersecting the bands and extending from one endof the stent to the other. The band-like elements are arrangedsequentially along the cylinder. Each band-like element has a generallyserpentine configuration to provide continuous waves of generallysinusoidal character to each band-like element. The waves arecharacterized by a plurality of peaks and troughs taking a generallylongitudinal direction along the cylinder. Midway between the peaks andtroughs is a midpoint region. Preferably, adjacent bands will be out ofphase with each other by 180°.

The plurality of spaced generally longitudinal elements have alternatingpeaks and troughs and longitudinal transition regions midway betweenadjacent peaks and troughs. Each generally longitudinal elementintersects each band like element in a region of intersection whichincludes a transition region of a longitudinal element and a midpointregion of a band. Each generally longitudinal element may, but need notbe substantially perpendicular to each band like element in each regionof intersection in the unexpanded stent. The longitudinal transitionregion of the longitudinal elements may be zig-zag shaped orsubstantially ‘S’ shaped.

The inventive stents are also designed so as to have desired shorteningor lengthening characteristics upon radial expansion. The exactshortening or lengthening characteristics will depend on the placementof the shanks relative to the midpoint positions on the band-likeelements between adjacent peaks and troughs. The midpoint position isdefined to be the position midway between an adjacent peak and trough ona band-like element. One such midpoint is designated by numeral 126 inFIG. 1. When the first shank of each link is attached to a band-likeelement between a midpoint and a peak (i.e. closer to a peak than to atrough) and the second shank of each link is attached to a band-likeelement between a midpoint and a trough (i.e. closer to a trough than toa peak), the stent is expected to shorten as the links are placed intension on expansion of the stent. If, on the other hand, the firstshank of each link is attached to a band-like element between a midpoint426 a and a trough 428 a and the second shank of each link is attachedto a band-like element between a midpoint 426 a and a peak 424 a, as inFIG. 7 a, the stent is expected to lengthen as the links are placed incompression on expansion of the stent. Of course, the exact lengtheningor shortening characteristics will depend on other properties as wellsuch as the material and construction including dimensions, geometry,morphology, configuration, functional behavior and mechanical behaviorof the stent and in particular, the links.

Although all of the stents, with the exception of that shown in FIGS. 7a and 7 b, are shown with links emanating from midway between the peakregion and the trough region of the band-like element, the inventioncontemplates the possibility of links emanating from anywhere betweenthe peak and the trough region of a band so as to control shortening andlengthening characteristics of the stent.

As already indicated, this invention is applicable to self-expandingconfigurations, mechanically expandable configurations and to stentsmade of a wide variety of materials, including metal, plastic and anyother material capable of functioning as an expandable stent. Forexample, the stent may be of metal wire or ribbon such as tantalum,stainless steel or the like or of metal sheeting or metal tubing. It maybe thin-walled. It may be of shape memory alloy such as Nitinol or thelike.

The figures disclosed herein are not intended to be limited to thestents shown but are further intended to convey equivalent structuressuch as stents which are the mirror images of an embodiment, and stentswhose patterns may derived from the patterns shown here via a variety ofsymmetry operations such as reflections, rotations and inversions andcombinations thereof about a given point, line or plane, as well asother equivalent structures.

The above Examples and disclosure are intended to be illustrative andnot exhaustive. These examples and description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

1-61. (Cancelled)
 62. A medical device comprising: a stent, the stentcomprising a hollow, cylindrical body comprised of a first ring and asecond ring, the first and the second rings each extendingcircumferentially around the cylindrical body, the first and secondrings each including an undulating series of peaks and valleys; a firstinflection point on the first ring, the first inflection point disposedon an intermediate portion of the first ring substantially centeredbetween an adjacent peak and valley, the first inflection pointincluding a portion extending generally circumferentially; a secondinflection point on the second ring, the second inflection pointdisposed on an intermediate portion of the second ring substantiallycentered between an adjacent peak and valley, the second inflectionpoint including a portion extending generally circumferentially; a linkjoined at a first end at the first inflection point on the first ringand at a second end at the second inflection point whereby the first andsecond rings are joined together.
 63. A medical device as in claim 1wherein the link includes at least two curved segments.
 64. A medicaldevice as in claim 1 wherein the portion of the inflection pointextending generally circumferentially has a length measuredcircumferentially which is substantially equal to a width of the link towhich it is attached.
 65. A medical device as in claim 1 wherein aportion of the link near its first end nests within the undulatingseries of peak and valleys of the first ring of the stent.
 66. A medicaldevice as in claim 1 wherein the undulating peaks and valleys of each ofthe first and second rings are formed by opposing curved segments joinedto each other by straight segments.
 67. A medical device as in claim 66wherein at least one of the straight segments is interrupted by aninflection point which produces a generally circumferentially offsetportion in the straight segment.
 68. A medical device as in claim 1wherein no more than one link is connected to either of the first andsecond inflection points.
 69. A medical device as in claim 1 wherein theundulating peaks and valleys of the first ring are arranged with theundulating peaks and valleys of the second ring such that the first andsecond rings appear as mirror images of each other.
 70. A medical deviceas in claim 1 wherein the undulating peaks and valleys the first ringare arranged with the undulating peaks and valleys of the second ringsuch that the first and second rings have peaks and valleys which arepaired with each other in an in-phase relationship.
 71. A medical deviceas in claim 1 wherein the first and second rings each include the samenumber of inflection points.
 72. A medical device as in claim 1 whereinthe first and second rings are joined by a plurality of links.
 73. Amedical device as in claim 13 wherein the plurality of links havecomplimentary shapes such that they will nest.
 74. A medical devicecomprising: a stent, the stent comprising a hollow, cylindrical bodycomprised of at least one ring, the ring extending circumferentiallyaround the cylindrical body, the ring including an undulating series ofpeaks and valleys; an inflection point on the ring, the inflection pointdisposed on an intermediate portion of the ring substantially centeredbetween an adjacent peak and valley; a first link joined at an end atthe inflection point.
 75. A medical device as in claim 74 wherein theinflection point includes a short portion extending generallycircumferentially.
 76. A medical device as in claim 75 wherein the shortportion of the inflection point extending generally circumferentiallyhas a length measured circumferentially which is substantially equal toa width of the link.
 77. A medical device as in claim 74 wherein thelink extends substantially parallel to a portion of the ring.
 78. Amedical device as in claim 74 wherein the link extends beyond a peak orvalley of the ring.
 79. A medical device as in claim 74 also comprisinga second link joined at an end at the inflection point and extendingfrom the inflection point in a direction substantially opposite to thefirst link.
 80. A medical device as in claim 79 wherein the first linkis joined at an upper portion of the inflection point and the secondlink is joined at a lower portion of the inflection point.
 81. A medicaldevice as in claim 79 wherein the first link is joined to the ring abovethe ring and the second link is joined to the ring below the ring.
 82. Amedical device as in claim 74 wherein a portion of the link nests withinthe undulating series of peaks and valleys of the ring.
 83. A medicaldevice as in claim 74 wherein the undulating peaks and valleys of thering are formed by opposing curved segments joined to each other bystraight segments.
 84. A medical device as in claim 83 wherein theinflection point forms an offset at at least one of the straightsegments to produce a generally circumferentially offset portion in thestraight segment.
 85. A medical device as in claim 74 wherein the ringincludes a plurality of inflection points and a plurality of linksjoined to the inflection points.
 86. A medical device as in claim 85wherein each peak and valley has an inflection point therebetween and afirst link joined at each inflection point.
 87. A medical device as inclaim 86 wherein each inflection point has a second link joined at eachinflection point and extending longitudinally opposite the first link.88. A medical device as in claim 86 wherein the plurality of links havecomplimentary shapes such that they will nest.